It is well known that compositions of matter formed into compact bodies from which the matter can be dissociated or released for various useful purposes are known. The release of material has many applications which may be readily apparent to persons skilled in the art of material release.
One such application is found in the medicinal use of drugs administered orally or otherwise into the organic system. Diffusion-controlled matrix devices have received a great deal of attention for drug delivery systems in the past years.
One approach has been to use insoluble porous disc matrices, in which the loading of the drug is greater than its solubility limit in the dissolution medium. However, it has been found that the amount of solute which diffuses out of these flat discs is linear with the square root of time. In other words, with this system, the amount of drug available at a biological site of absorption decreases as a function of time if the absorption rate is greater than the drug release rate from the matrix.
One way to overcome this difficulty has been to vary the matrix geometry in order to ideally attain a zero-order drug release. With this thought in mind, it was suggested that a sector of a right circular cylinder could be the needed geometry. Dean S. T. Hshich and some of his colleagues in the Journal of Pharmaceutical Sciences, vol. 72, no. 1, January 1983, proposed a hemispheric structure. However, in order to adapt these systems for pharmaceutical manufacturing, considerable modifications in their fabrication procedure would have to be carried out.
Recently, it was suggested by Wei-Youh K. et al., in the Journal of Pharmaceutical Sciences, vol. 74, no. 9, September 1985, that a multiple-hole system might provide a near zero-order-release but this suggestion has not been proved efficient by any experimental data.